Dry boxing a cigar takes some experience, there's a 'feel' to it based on a few elements. Like Danny mentioned, a day or two can make all the difference in the cigar's taste.
The factors involved are...
1) How moist is the cigar to begin with?
2) How 'dry' is your dry box? (I use an extra desktop for mine too)
3) What is the ambient humidity in the room your dry box is in?
4) What kind of cigar are you dry boxing? ex: CC smoke better in the 60-64% zone...Nicaraguans smoke better at 65-70%...that's based on MY TASTES.
It takes some time to learn to dry box when you factor in the above info...and in the end, it's all based on your taste and a bit of guessing. The effects of dry boxing is quicker in the Winter versus the Summer due to the lack of ambient moisture in the air and the opposite in the Summer. I don't re-humidify my dry box humidor ever, Once in a while I'll leave it open in the Summer (without cigars in it) to absorb the ambient moisture in the air and that is suffice for me. I also find I don't dry box as much in the Winter.
If you can find an old desktop humidor to use for this purpose, keep a hygrometer in it to monitor the moisture. If it's at 57%, and you're putting in a pretty moist cigar, you'll eventually figure out for how long it will take to 'de-humidify' the cigar to your liking....that's where the skill comes in. If the humidity is lower in there, say 45%, it will take less time. Once you understand the elements involved, it's 'smoke it and figure it out' time...there is no definitive dry box instructions that any of us can give you stating hard numbers.
Just keep experimenting and make mental notes as you go along, in time, you'll get good at it once you realize everything involved. Hell, I've been known to put a Post-it Note on top of my dry box so I don't forget I put cigars in there...or so I don't forget what day I put them in!
:laugh: